This invention relates generally to radioactive seed therapy for prostate cancer and possibly other cancers, and more particularly concerns the determination of the position of radioactive seed and dosimetry in needles after the seeds have been loaded into the needles.
In radioactive seed therapy for prostate cancer, referred to as brachytherapy, hollow stainless steel needles, typically 15 to 19 gauge, are loaded with cylindrical radioactive pellets, separated by inert spacers in a preselected pattern. The seed pattern is the result of a pre-procedure dosimetry plan to treat the prostate cancer in a given patient. The dosimetry plan is produced by ultrasound investigation of the prostate, identifying the location and configuration of the cancer within the prostate. The radioactive pellets are usually iodine #125 and/or palladium #103.
After the radioactive seeds have been loaded in the conventional stainless steel needles in the preselected pattern, it is not possible by visual inspection to verify the seed pattern and confirm that it is the correct pattern for that particular needle and/or whether the seeds have the desired radioactive strength. Such verification is in fact important in the overall treatment process, since errors do occur in loading and since sometimes the seeds are below the acceptable range of radioactive strength. To verify the radioactive seed pattern with conventional techniques, the loaded needle, prior to insertion in the prostate, is used to expose an X-ray film pack which is then developed and the resulting exposure compared with the dosimetry plan. However, this X-ray-based technique takes a substantial amount of time, is inconvenient and subject to error and thus is often not used.
Accordingly, it is desirable that a system be developed for conveniently and quickly verifying the radioactive seed pattern in loaded brachytherapy needles prior to use thereof.
Accordingly, the present invention is an apparatus for determining the position of radioactive seeds in a loaded needle, comprising: a pickup unit into which the loaded needle is positioned, the pickup unit including a detector element, such as a scintillating (phosphor) screen, positioned so as to be responsive to the radioactive energy from the seeds in the needle to produce a corresponding light output, the pickup unit further including an optical pickup assembly responsive to said light output to produce corresponding output information; and a display assembly, including a processor, responsive to the output information to produce a visual indication of the pattern of radioactive seeds in the needle, permitting convenient comparison with a preselected pattern of radioactive seeds therein.